CN103984868B - A kind of oxygen-enriched combustion boiler thermal performance acquisition methods - Google Patents

Abstract

The invention discloses a kind of oxygen-enriched combustion boiler thermal performance acquisition methods, comprise step: the burning calculating of fuel, flue gas and air-supply simulation, heat Balance Calculation, burner hearth thermodynamic computing and convection heating surface thermodynamic computing, calculating flame blackness wherein in burner hearth thermodynamic computing and furnace emissivity step, and calculate flue gas blackness in convection heating surface thermodynamic computing and determine fume side radiant heat-transfer coefficient step, its three atomic gas radiative absorption coefficient k adopted _yaccording to calculate, wherein P _h2Ofor H in flue gas ₂o partial pressure; S is radiating layer net thickness; ε is three atomic gas emissivity.Oxygen-enriched combustion boiler thermal performance acquisition methods provided by the invention, it is more accurate to obtain for oxygen-enriched combustion boiler thermal performance, and its precision can reach design and check the demand of oxygen-enriched combustion boiler thermal performance.

Description

Method for acquiring thermal performance of oxygen-enriched combustion boiler

Technical Field

The invention belongs to the field of boiler thermal performance design, and particularly relates to a method for correcting the thermal performance of an oxygen-enriched combustion boiler.

Background

In the design process of the boiler, the thermal performance of the boiler needs to be acquired, so that hydrodynamic design, compression element strength design, ventilation resistance design, furnace wall thermal design, pipe wall temperature design, powder making system design, aerodynamic design and the like are performed, and the thermal performance data of the boiler is the core of the overall design of the boiler and is the basic basis for boiler design, check and operation.

The boiler performance acquisition process usually includes performing flue gas and air supply simulation on a given boiler from fuel combustion calculation, so as to perform heat balance calculation, and performing hearth thermodynamic calculation and convection heating surface thermodynamic calculation on the boiler according to the heat balance calculation result, so as to obtain thermodynamic performance data of each heating surface. The existing method for acquiring the thermal performance of the boiler is established aiming at the conventional air combustion atmosphere, and comprises the 1957 edition standard and the 1973 edition standard of the former Soviet Union, the ASME standard of the United states and the like.

At present, a boiler of a novel combustion mode, i.e., an oxygen-enriched combustion atmosphere combustion boiler, has been developed. The existing boiler thermodynamic calculation method cannot acquire thermodynamic performance aiming at the novel combustion boiler.

Disclosure of Invention

Aiming at the defects or the improvement requirements in the prior art, the invention provides a thermal performance acquisition method, and aims to design a set of thermal performance acquisition method aiming at a combustion boiler in oxygen-enriched combustion atmosphere, so that the technical problem that the conventional boiler thermal performance acquisition method cannot adapt to a novel oxygen-enriched combustion boiler is solved.

In order to achieve the above object, according to one aspect of the present invention, a method for obtaining thermal performance of an oxygen-enriched combustion boiler is provided, which includes steps of fuel combustion calculation, flue gas and air supply simulation, heat balance calculation, hearth thermal calculation and convection heating surface thermal calculation.

Wherein, furnace thermodynamic calculation includes the step:

(A1) calculating the structural size of a hearth and the thickness of a relative radiation layer of the flue gas;

(A2) selecting the temperature of hot air, and calculating the effective heating value of each kilogram of fuel entering a hearth;

(A3) calculating the central position coefficient of the flame according to the general fuel class, the combustion equipment form and the arrangement mode;

(A4) estimating the temperature of the smoke at the outlet of the hearth, and calculating the average heat capacity of the smoke of the hearth;

(A5) calculating the radiation heat exchange characteristic parameter of the heating surface of the hearth;

(A6) calculating flame blackness and hearth blackness according to fuel and a combustion mode;

(A7) calculating and checking the temperature of the flue gas at the outlet of the hearth;

(A8) checking the error of the temperature of the smoke at the outlet of the hearth;

(A9) calculating the thermal parameters of the hearth;

(A10) calculating heat exchange of other radiation heating surfaces in the hearth;

the convection heating surface thermodynamic calculation comprises the following steps:

(B1) estimating the temperature of flue gas at the outlet of the heating surface, and checking a corresponding enthalpy value;

(B2) calculating the convection heat transfer quantity according to the outlet smoke enthalpy;

(B3) according to the principle that the side heat release quantity of the flue gas is equal to the side heat absorption quantity of the working medium, the enthalpy value and the corresponding temperature of the working medium outlet are obtained;

(B4) calculating the average convection heat transfer temperature difference;

(B5) calculating the convection heat release coefficient of the flue gas side and the pipe wall fouling coefficient;

(B6) calculating the convection heat release coefficient of the working medium side;

(B7) calculating the temperature of the pipe wall fouling layer;

(B8) calculating the blackness of the flue gas and determining the radiation heat release coefficient of the flue gas side;

(B9) calculating the total convection heat release coefficient;

(B10) the convective heat transfer was calculated.

The radiation attenuation coefficient of the three-atom gas adopted in the steps (A6) and (B8) is the radiation attenuation coefficient k of the three-atom gas aiming at the oxygen-enriched environment_yInstead, it is calculated according to the following formula:

$k_y=-\frac{\mathrm{Ln}(1-\mathrm{\ϵ})}{P_{H2O}S}$

wherein, P_H2OFor H in flue gas₂Partial pressure of O; s is the effective thickness of the radiation layer; is the triatomic gas emissivity. Under the conditions of a certain temperature T and the effective thickness S of the radiation layer, the emissivity of the three-atom gas is calculated according to the following formula:

$\mathrm{\ϵ}(T,S)=\underset{j=1}{\overset{4}{\mathrm{\Σ}}}{\mathrm{\α}}_j\left(T\right)(1-e^{-(p_{\mathrm{co}2}+p_{H2o})k_j(T,\mathrm{\Φ})100S})$

${\mathrm{\α}}_j\left(T\right)=\underset{i=1}{\overset{4}{\mathrm{\Σ}}}{c}_{j,i}{\left(\frac{T}{T_{\mathrm{ref}}}\right)}^{I-i}$

$k_j\left(T\right)=\underset{i=1}{\overset{4}{\mathrm{\Σ}}}{b}_i{\left(\frac{T}{T_{\mathrm{ref}}}\right)}^{I-i}$

wherein p is_co2Is the partial pressure of carbon dioxide gas, P_H2OIs the water vapor partial pressure; phi is the partial pressure ratio of water vapor to carbon dioxide, phi is P_H2O/P_CO2；T_ref1000K; t is the average Kelvin temperature of the flue gas; j is an integer, and j is more than or equal to 1 and less than or equal to 4.

Preferably, the method for obtaining the thermodynamic performance of the oxygen-enriched combustion boiler comprises the steps of simulating the existing flue gas and air supply, replacing the simulation with the balance calculation of the oxygen-enriched flue gas and air, wherein the balance calculation of the oxygen-enriched flue gas and air is carried out according to the selected circulation multiplying power, the air separation oxygen production purity, the peroxide coefficient, the air leakage coefficient, the condensed water vapor content, the primary air share, the primary hot air share and the primary air oxygen injection ratio, setting the initialized flue gas amount and the iteration times according to the fuel components, obtaining the flue gas amount, the smoke exhaust amount, the circulation flue gas amount, the combustion-supporting gas primary air amount, the combustion-supporting gas secondary air amount, the air supply amount and the air leakage amount of the air separation device by adopting the method of iteration calculation, and finally obtaining the flue gas amount, the smoke exhaust amount, the circulation flue gas amount, the combustion-supporting gas primary air amount.

Preferably, in the method for obtaining the thermal performance of the oxyfuel combustion boiler, the ith iterative calculation process is as follows:

amount of circulating flue gas V_ref：

V_ref＝V_i-1×R^r

Wherein, V_i-1Is the smoke amount obtained by the last iteration calculation, and when i is equal to 1, V is_i-1The initial smoke amount; r^rThe circulation multiplying power is adopted;

flue gas volume V_i：

$V_i=(1+{\mathrm{\α}}_{1f})(V_{\mathrm{ll}}+V_{\mathrm{ref}}+V_{o2}^0)$

Wherein, α_lfThe air leakage coefficient is preferably less than 0.02; v_llThe calculation method of the theoretical smoke quantity generated by boiler combustion is shown in boiler thermodynamic calculation standard 1973 edition; v_refThe amount of the circulating flue gas is;the theoretical oxygen demand is calculated as follows:

$V_{o2}^0=1.866\frac{C_{\mathrm{ar}}}{100}+5.56\frac{H_y}{100}+0.7\frac{S_y}{100}-0.7\frac{O_y}{100}$

wherein, Car, Har, Nar, Oar and Sar are the received base components of various elements in the fuel respectively;

discharge amount V_py：

V_py＝V_i-V_ref-V_lns

Wherein, V_lnsIs the water vapor content after condensation;

primary air volume V of combustion-supporting gas_zr1：

V_zr1＝β₁×V_ref

Combustion-supporting gas secondary air volume V_zr2：

V_zr2＝(1-β₁)×V_ref

Wherein, β₁Is the primary air share;

air supply volume V of air separation device_kf：

$V_{\mathrm{kf}}=(V_{o2}-V_{o2}^{\mathrm{zr}})/\mathrm{\γ}$

Wherein, V_o2The oxygen demand of the oxygen-enriched combustion boiler is obtained;the oxygen content originally contained in the combustion-supporting gas; gamma is the air separation oxygen production purity; oxygen demand V of oxygen-enriched combustion boiler_o2The calculation formulas of (A) and (B) are respectively as follows:

oxygen demand V of oxygen-enriched combustion boiler_o2The calculation formula of (a) is as follows:

$V_{o2}={\mathrm{\α}}_{\mathrm{gy}}\×V_{o2}^0$

wherein, α_gyIs the peroxide coefficient;theoretical oxygen demand;

air leakage rate V_lfThe calculation formula of (a) is as follows:

V_lf＝α_lf×V_o

wherein, α_lfThe value of the air leakage coefficient is less than 0.02V_oThe calculation method is as follows for the amount of the flue gas at the outlet of the hearth:

$V_o=V_{\mathrm{ll}}+V_{\mathrm{zrl}}+V_{\mathrm{zr}2}-V_{O2}^0$

wherein, V_llThe calculation method of the theoretical smoke quantity generated by boiler combustion is shown in boiler thermodynamic calculation standard 1973 edition; v_zr1The primary air quantity of combustion-supporting gas, V_zr2The secondary air quantity of the combustion-supporting gas,is the theoretical requirement;

the gas leaking into the furnace chamber contains N₂、O₂、H₂O, the content of each component is calculated as follows:

$V_{N2}^{\mathrm{lf}}=0.79\×V_{\mathrm{lf}}$

$V_{O2}^{\mathrm{lf}}=0.21\×V_{\mathrm{lf}}$

$V_{N2o}^{\mathrm{lf}}=0.161\×V_{\mathrm{lf}}$

wherein,respectively N leaking into the furnace₂、O₂、H₂The volume of O;

preferably, the method for obtaining the thermal performance of the oxyfuel combustion boiler is that when the heat transfer capacity of the convection heating surface is calculated, the convection heat transfer coefficient is calculated according to the following formula:

${\mathrm{\α}}_d=0.2C_z{C}_s\frac{\mathrm{\λ}}{d}{\left(\frac{\mathrm{\ωd}}{v}\right)}^{0.65}{P_r}^{0.33}$

wherein, C_z、C_sFor correcting the coefficient, the calculation method refers to the boiler thermodynamic calculation standard (1973 edition), and lambda is the heat conductivity coefficient of the flue gas; d is the pipe diameter; omega is the flow rate of the flue gas; v is kinematic viscosity; pr is the prandtl number.

Preferably, the thermal performance obtaining method of the oxygen-enriched combustion boiler comprises the following steps of calculating the kinematic viscosity v and the prandtl number Pr according to the following formula:

$v=\mathrm{\μ}\frac{R_{g}T}{p}$

$P_r=\frac{\mathrm{\μ}{C}_p}{\mathrm{\λ}}$

wherein mu is the dynamic viscosity of the flue gas, R_gIs the gas constant, T is the Kelvin temperature, p is the flue gas pressure, C_pThe specific heat capacity is the constant pressure of the flue gas, and the lambda is the heat conductivity coefficient of the flue gas.

Preferably, the method for obtaining the thermal performance of the oxygen-enriched combustion boiler comprises the steps of obtaining the dynamic viscosity mu of the flue gas and the specific heat capacity C of the flue gas at constant pressure_pThe fitting method comprises the following steps:

smoke dynamic viscosity μ:

$\mathrm{\μ}=\frac{\mathrm{\Σ}{y}_i{\mathrm{\μ}}_i{M}_i^{\frac{1}{2}}}{\mathrm{\Σ}{y}_i{M}_i^{\frac{1}{2}}}$

flue gas constant pressure specific heat capacity C_p：

Heat conductivity of flue gas λ:

$\mathrm{\λ}=\frac{\mathrm{\Σ}{y}_i{\mathrm{\λ}}_i{M}_i^{\frac{1}{3}}}{\mathrm{\Σ}{y}_i{M}_i^{\frac{1}{3}}}$

wherein, mu_iIs the kinetic viscosity of the pure i component under normal pressure; lambda [ alpha ]_iThe thermal conductivity coefficient of the pure i component under normal pressure; m_iIs the molar mass of the i component in the mixture; y is_iIs the mole fraction or volume fraction of the i component in the mixture.

In general, compared with the prior art, the method for acquiring the thermal performance of the oxygen-enriched combustion boiler provided by the invention redesigns the three-atom gas radiation attenuation coefficient, the convective heat transfer coefficient and the oxygen-enriched smoke and air balance calculation aiming at the oxygen-enriched combustion atmosphere, so that the thermal performance of the oxygen-enriched combustion boiler is acquired more accurately, and the precision can meet the requirement of designing and checking the thermal performance of the oxygen-enriched combustion boiler.

Drawings

FIG. 1 is a schematic diagram of a method for obtaining thermal performance of an oxycombustion boiler provided by the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The method for acquiring the thermal performance of the oxygen-enriched combustion boiler, disclosed by the invention, is characterized in that as shown in figure 1, the existing flue gas and air supply are simulated and replaced by the balance calculation of oxygen-enriched flue gas and air; obtaining the heat efficiency of the boiler and the effective utilization heat of the working medium of the boiler, namely the fuel consumption of the boiler according to the prior heat balance calculation of the boiler; performing hearth thermodynamic calculation and convection heating surface thermodynamic calculation according to the existing steps, wherein the radiation attenuation coefficient of the triatomic gas is replaced by the radiation attenuation coefficient of the triatomic gas aiming at the oxygen-enriched environment; the convective heat transfer coefficient is replaced by the convective heat transfer coefficient aiming at the oxygen-enriched combustion environment.

The oxygen-enriched combustion boiler comprises a cold-dry cycle type boiler, a cold-wet cycle type boiler and a heat cycle type boiler, wherein the three oxygen-enriched combustion boilers all adopt a balanced ventilation mode, the oxygen-enriched smoke-air balance calculation is that the initial smoke amount and the iteration times are set according to the selected cycle multiplying power, the air separation oxygen production purity, the peroxide coefficient, the air leakage coefficient, the condensed water vapor content, the primary air share, the primary hot air share and the primary air oxygen injection ratio, and the smoke amount, the smoke exhaust amount, the cycle smoke amount, the combustion-supporting gas primary air amount, the combustion-supporting gas secondary air amount, the air supply amount and the air leakage amount of an air separation device are obtained by adopting an iterative calculation method. The iteration frequency is preferably 100 to 1000 times, and the obtained flue gas volume, the smoke discharge volume, the circulating flue gas volume, the combustion-supporting gas primary air volume, the combustion-supporting gas secondary air volume, the air supply volume and the air leakage volume of the air separation device obtained by the last iteration calculation are final results. Cycling multiplying power; air separation oxygen production purity, preferably in the range of 97% to 99%; peroxide coefficient, preferably in the range of 1.05 to 1.3; leakage coefficient, preferably not more than 0.02; the water vapor content after condensation is from 3% to 5%, preferably in the range from 3% to 5%; primary air share; the hot wind share in the primary wind; so that the oxygen injection proportion of the primary air is less than 21 percent.

The ith iterative calculation procedure is as follows:

amount of circulating flue gas V_ref：

V_ref＝V_i-1×R^r

Wherein, V_i-1Is the smoke amount obtained by the last iteration calculation, and when i is equal to 1, V is_i-1The initial smoke amount; r^rIs a cyclic magnification

Flue gas volume V_i：

$V_i=(1+{\mathrm{\α}}_{1f})(V_{\mathrm{ll}}+V_{\mathrm{ref}}+V_{o2}^0)$

Wherein, α_lfThe air leakage coefficient is preferably less than 0.02; v_llThe calculation method of the theoretical smoke quantity generated by boiler combustion is shown in boiler thermodynamic calculation standard 1973 edition; v_refThe amount of the circulating flue gas is;the theoretical oxygen demand is calculated as follows:

$V_{o2}^0=1.866\frac{C_{\mathrm{ar}}}{100}+5.56\frac{H_y}{100}+0.7\frac{S_y}{100}-0.7\frac{O_y}{100}$

wherein, Car, Har, Nar, Oar and Sar are the received base compositions of various elements in the fuel respectively.

Discharge amount V_py：

V_py＝V_i-V_ref-V_lns

Wherein, V_lnsIs the water vapor content after condensation.

Primary air volume V of combustion-supporting gas_zr1：

V_zr1＝β₁×V_ref

Combustion-supporting gas secondary air volume V_zr2：

V_zr2＝(1-β₁)×V_ref

Wherein, β₁Is the primary air fraction.

Air supply volume V of air separation device_kf：

$V_{\mathrm{kf}}=(V_{o2}-V_{o2}^{\mathrm{zr}})/\mathrm{\γ}$

Wherein, V_o2The oxygen demand of the oxygen-enriched combustion boiler is obtained;the oxygen content originally contained in the combustion-supporting gas; gamma is the air separation oxygen production purity, the value is between 90% and 99.9%, and the impurity gas in oxygen is argon and nitrogen; oxygen content originally contained in the combustion-supporting gasOxygen demand V of oxygen-enriched combustion boiler_o2The calculation formulas of (A) and (B) are respectively as follows:

oxygen demand V of oxygen-enriched combustion boiler_o2The calculation formula of (a) is as follows:

$V_{o2}={\mathrm{\α}}_{\mathrm{gy}}\×V_{o2}^0$

wherein, α_gyThe excess oxygen coefficient is different from the excess air coefficient under the air atmosphere, the selection of the excess oxygen coefficient not only ensures the complete combustion of the pulverized coal in a hearth, but also gives consideration to the economy, and the value range of the excess oxygen coefficient is 1.05-1.3;is the theoretical oxygen demand.

Air leakage rate V_lfThe calculation formula of (a) is as follows:

V_lf＝α_lf×V_o

wherein, α_lfThe value of the air leakage coefficient is less than 0.02; v_oThe calculation method is as follows for the amount of the flue gas at the outlet of the hearth:

$V_o=V_{\mathrm{ll}}+V_{\mathrm{zrl}}+V_{\mathrm{zr}2}-V_{O2}^0$

wherein, V_llThe calculation method of the theoretical smoke quantity generated by boiler combustion is shown in boiler thermodynamic calculation standard 1973 edition; v_zr1The primary air quantity of combustion-supporting gas, V_zr2The secondary air quantity of the combustion-supporting gas,is the theoretical requirement.

The gas leaking into the furnace chamber contains N₂、O₂、H₂O, the content of each component is calculated as follows:

$V_{N2}^{\mathrm{lf}}=0.79\×V_{\mathrm{lf}}$

$V_{O2}^{\mathrm{lf}}=0.21\×V_{\mathrm{lf}}$

$V_{N2o}^{\mathrm{lf}}=0.161\×V_{\mathrm{lf}}$

wherein,respectively N leaking into the furnace₂、O₂、H₂Volume of O.

The hearth thermodynamic calculation is to calculate the temperature of the smoke at the outlet of the hearth according to the structural data of the hearth, the form and the arrangement mode of combustion equipment, the selected hot air temperature and the selected fuel components. The calculation method is referred to boiler thermodynamic calculation standard (1973 edition), and comprises the following steps:

(A1) calculating the structural size of a hearth and the thickness of a relative radiation layer of the flue gas;

(A2) selecting the temperature of hot air, and calculating the effective heating value of each kilogram of fuel entering a hearth;

(A3) calculating the central position coefficient of the flame according to the general fuel class, the combustion equipment form and the arrangement mode;

(A4) estimating the temperature of the smoke at the outlet of the hearth, and calculating the average heat capacity of the smoke of the hearth;

(A5) calculating the radiation heat exchange characteristic parameter of the heating surface of the hearth;

(A6) calculating flame blackness and hearth blackness according to fuel and a combustion mode;

(A7) calculating and checking the temperature of the flue gas at the outlet of the hearth;

(A8) checking the error of the temperature of the smoke at the outlet of the hearth;

(A9) calculating the thermal parameters of the hearth;

(A10) and (4) calculating heat exchange of other radiation heating surfaces in the hearth.

Wherein when the flame blackness and the hearth blackness are calculated in the step (A6), the radiation attenuation coefficient k of the three-atom gas aiming at the oxygen-enriched environment is used_yThe method replaces the existing three-atom gas radiation attenuation coefficient calculation method provided by the boiler thermodynamic calculation standard, and comprises the following steps:

$k_y=-\frac{\mathrm{Ln}(1-\mathrm{\ϵ})}{P_{H2O}S}$

wherein, P_H2OFor H in flue gas₂Partial pressure of O; s is the effective thickness of the radiation layer; is the triatomic gas emissivity. Under the conditions of a certain temperature T and the effective thickness S of the radiation layer, the emissivity of the three-atom gas is calculated according to the following formula:

$\mathrm{\ϵ}(T,S)=\underset{j=1}{\overset{4}{\mathrm{\Σ}}}{\mathrm{\α}}_j\left(T\right)(1-e^{-(p_{\mathrm{co}2}+p_{H2o})k_j(T,\mathrm{\Φ})100S})$

${\mathrm{\α}}_j\left(T\right)=\underset{i=1}{\overset{4}{\mathrm{\Σ}}}{c}_{j,i}{\left(\frac{T}{T_{\mathrm{ref}}}\right)}^{I-i}$

$k_j\left(T\right)=\underset{i=1}{\overset{4}{\mathrm{\Σ}}}{b}_i{\left(\frac{T}{T_{\mathrm{ref}}}\right)}^{I-i}$

wherein p is_co2Is the partial pressure of carbon dioxide gas, P_H2OPreferred P for the partial pressure of water vapor in the invention_H2O+P_CO21 is ═ 1; phi is the partial pressure ratio of water vapor to carbon dioxide, phi is P_H2O/P_CO2，0.125≤Φ≤1；T_ref1000K; t is the average Kelvin temperature of the flue gas; j is independent variable, j is more than or equal to 1 and less than or equal to 4.

The convection heating surface thermodynamic calculation comprises the following steps: the device comprises a screen superheater, a convection superheater, a reheater, an economizer, a combustion-supporting gas preheater and a convection bank. The heat calculation of the convection heating surface is to calculate the heat transfer capacity of the convection heating surface according to the temperature of the flue gas at an inlet and an outlet and the structural data of the convection heating surface, and comprises the following steps:

(B1) estimating the temperature of flue gas at the outlet of the heating surface, and checking a corresponding enthalpy value;

(B2) calculating the convection heat transfer quantity according to the outlet smoke enthalpy;

(B3) according to the principle that the side heat release quantity of the flue gas is equal to the side heat absorption quantity of the working medium, the enthalpy value and the corresponding temperature of the working medium outlet are obtained;

(B4) calculating the average convection heat transfer temperature difference;

(B5) calculating the convection heat release coefficient of the flue gas side and the pipe wall fouling coefficient;

(B6) calculating the convection heat release coefficient of the working medium side;

(B7) calculating the temperature of the pipe wall fouling layer;

(B8) calculating the blackness of the flue gas and determining the radiation heat release coefficient of the flue gas side;

(B9) calculating the total convection heat release coefficient;

(B10) calculating the convection heat transfer quantity;

when the heat transfer quantity of the convection heating surface is calculated in the step (B5), the convection heat transfer coefficient is calculated according to the following formula:

${\mathrm{\α}}_d=0.2C_z{C}_s\frac{\mathrm{\λ}}{d}{\left(\frac{\mathrm{\ωd}}{v}\right)}^{0.65}{P_r}^{0.33}$

wherein, C_z、C_sFor correcting the coefficient, the calculation method refers to the boiler thermodynamic calculation standard (1973 edition), and lambda is the heat conductivity coefficient of the flue gas; d is the pipe diameter; omega is the flow rate of the flue gas; v is kinematic viscosity; pr is the prandtl number. The kinematic viscosity v and the Plantt number Pr are calculated according to the following formula:

$v=\mathrm{\μ}\frac{R_{g}T}{p}$

$P_r=\frac{\mathrm{\μ}{C}_p}{\mathrm{\λ}}$

wherein mu is the dynamic viscosity of the flue gas, R_gIs the gas constant, T is the Kelvin temperature, p is the flue gas pressure, C_pThe specific heat capacity is the constant pressure of the flue gas, and the lambda is the heat conductivity coefficient of the flue gas. The smoke property changes violently due to the fact that smoke components change greatly, and the calculation method which considers that the smoke components are unchanged at present has large calculation errors and cannot meet the calculation accuracy requirement. The invention provides a method for fitting smoke physical property parameters according to smoke components, and the calculation result is within an engineering error allowable range. The specific process is as follows:

smoke dynamic viscosity μ:

$\mathrm{\μ}=\frac{\mathrm{\Σ}{y}_i{\mathrm{\μ}}_i{M}_i^{\frac{1}{2}}}{\mathrm{\Σ}{y}_i{M}_i^{\frac{1}{2}}}$

flue gas constant pressure specific heat capacity C_p：

C_p＝y_iC_pi

Heat conductivity of flue gas λ:

$\mathrm{\λ}=\frac{\mathrm{\Σ}{y}_i{\mathrm{\λ}}_i{M}_i^{\frac{1}{3}}}{\mathrm{\Σ}{y}_i{M}_i^{\frac{1}{3}}}$

wherein, mu_iIs the kinetic viscosity of the pure i component under normal pressure; lambda [ alpha ]_iThe thermal conductivity coefficient of the pure i component under normal pressure; m_iIs the molar mass of the i component in the mixture; y is_iIs the mole fraction or volume fraction of the i component in the mixture.

Physical property parameters of each component of the flue gas are as follows: heat conductivity coefficient lambda of each component of flue gas_iGas dynamic viscosity mu of each component of the smoke_iConstant pressure specific heat capacity C of each component of flue gas_piFit against NIST database.

Wherein the three-atom gas radiation attenuation coefficient adopted in the step (B8) is the same as the three-atom gas radiation attenuation coefficient adopted in the step (A6) and is the three-atom gas radiation attenuation coefficient k aiming at the oxygen-enriched environment_y。

The following are examples:

example 1

The method for checking the thermal performance of the oxygen-enriched combustion boiler provided by the invention checks the cold dry cycle type oxygen-enriched combustion boiler:

the boiler to be checked is a cold dry circulating type oxygen-enriched combustion boiler. The design requirement is as follows: see "boiler thermodynamic calculation Standard" (1973 edition)

The operation parameters of the boiler to be checked are shown in the table 1; the coal quality parameters are shown in Table 2.

TABLE 1 boiler operating parameters

Maximum continuous evaporation capacity	t/h	695
			Superheater outlet steam pressure	MPa.(a)	13.4
Superheater outlet steam temperature	℃	538
			Reheat steam flow	t/h	595
Reheater inlet steam pressure	MPa.(a)	3
			Reheater inlet steam temperature	℃	331
Reheater outlet steam pressure	MPa.(a)	2.85
			Reheater outlet steam temperature	℃	538
Temperature of feed water	℃	255

TABLE 2 coal quality parameters

And selecting boiler design parameters.

Under the oxygen-enriched combustion cold-dry circulating atmosphere, the circulating multiplying power is 0.697; the purity of the air separation oxygen generation gas is 97 percent; the peroxide coefficient is 1.15; the leakage coefficient is 0.02; the water vapor content after condensation is 5 percent; primary air share; the hot wind share in the primary wind; the oxygen injection proportion of the primary air is 18 percent.

And (3) smoke and wind balance calculation: initializing the smoke amount: 7.613Nm³Kg, number of iterations: 500, a step of; and (3) iterative calculation results: flue gas volume V₁：6.011Nm³Per kg; amount of discharged smoke1.363Nm³Per kg; circulating flue gasMeasurement of4.187Nm³Per kg; primary air quantity of combustion-supporting gas1.325Nm³Per kg; secondary air quantity of combustion-supporting gas4.171Nm³Per kg; air supply volume V of air separation device_kf：1.309Nm³/kg。

Thermodynamic calculation of each heating surface: platen superheater: error is-0.79%; convection superheater: the error is 0.03%; a reheater: error is-0.43%; a coal economizer: the error is 0.23%; convection bank: the error is 1.05%; total heat transfer: the error was-0.13%.

All meet the design requirements.

Example 2:

the design requirements of the cold-dry circulation type oxygen-enriched combustion boiler are shown in the step (1); the results of the calculations are as follows,

under the oxygen-enriched combustion cold-wet circulating atmosphere, the circulating multiplying power is 0.710; the purity of the air separation oxygen-making gas is 98 percent; the peroxide coefficient is 1.2; a leakage coefficient of 0.015; the water vapor content after condensation is 4 percent; primary air fraction, 0.233; the hot wind share in the primary wind is 0.7; the oxygen injection proportion of the primary air is 18 percent.

Initializing the smoke amount: 7.613Nm³Kg, number of iterations: 500, a step of; and (3) calculating the result: flue gas volume V₁：6.223Nm³Per kg; amount of discharged smoke1.331Nm³Per kg; amount of circulating flue gas4.417Nm³Per kg; primary air quantity of combustion-supporting gas1.336Nm³Per kg; secondary air quantity of combustion-supporting gas4.399Nm³Per kg; air supply volume V of air separation device_kf：1.318Nm³/kg

Example 3:

under the oxygen-enriched combustion heat circulation atmosphere, the circulation multiplying power is 0.678; the purity of the air separation oxygen-making gas is 97.5 percent; the peroxide coefficient is 1.05; leakage coefficient 0.01; the water vapor content after condensation is 3 percent; primary air fraction, 0.266; the hot wind share in the primary wind is 0.7; the oxygen injection proportion of the primary air is 18 percent.

Initializing the smoke amount: 7.613Nm³Kg, number of iterations: 500, a step of; and (3) calculating the result: flue gas volume V₁：5.523Nm³Per kg; amount of discharged smoke1.291Nm³Per kg; amount of circulating flue gas3.742Nm³Per kg; primary air quantity of combustion-supporting gas1.337Nm³Per kg; secondary air quantity of combustion-supporting gas3.681Nm³Per kg; air supply volume V of air separation device_kfThe following steps: 1.276Nm³/kg。

The thermodynamic calculation conditions of each heating surface are as follows: platen superheater: error is-1.02%; convection superheater: error is-0.34%; a reheater: the error is 0.25%; a coal economizer: error is-0.79%; convection bank: error is-0.96%; total heat transfer: the error was-0.04%.

All meet the design requirements.

Example 4

Under the oxygen-enriched combustion cold-dry circulating atmosphere, the purity of oxygen is 97%, the peroxide coefficient is 1.15, the leakage coefficient is 0.02, the primary air oxygen injection proportion is 18%, when the circulating multiplying power value is 0.697, the oxygen partial pressure in the total gas sent into the hearth is 26%, and the calculation result is counted into the total gas after air leakage, namely CO₂74.6% of water vapor, 12.3% of O₂3.5% of nitrogen, 9.4% of SO₂Content 0.251%, after dehydration, CO₂The concentration is 80.8 percent, the emissivity of the three-atom gas of the high-temperature superheater is 0.276, the radiation attenuation coefficient of the three-atom gas is 4.9, the blackness of the flue gas is 0.35, and the radiation heat transfer coefficient of the flue gas is 105.6w/m²·℃。

Example 5

Under the oxygen-enriched combustion cold-wet circulating atmosphere, the purity of oxygen is 97%, the peroxide coefficient is 1.15, the leakage coefficient is 0.02, the oxygen injection proportion of primary air is 18%, when the circulating multiplying power is 0.664, the oxygen partial pressure in the total gas sent into a hearth is 29%, and the calculation result is counted in the total gas after air leakage, namely CO₂68.2% of water vapor, 3.8% of oxygen, 8% of nitrogen and SO₂Content 0.23%, after dehydration, CO₂The concentration is 81 percent, the emissivity of the three-atom gas of the high-temperature superheater is 0.301, the radiation attenuation coefficient of the three-atom gas is 5.37, the blackness of the flue gas is 0.38, and the radiation heat transfer coefficient of the flue gas is 110.5w/m²·℃。

Example 6

Under the oxygen-enriched combustion thermal cycle atmosphere, the purity of the oxygen is 97 percentThe oxygen coefficient is 1.15, the leakage coefficient is 0.02, the oxygen injection proportion of primary air is 18%, when the circulation multiplying power is 0.696, the oxygen partial pressure in the total gas sent into the hearth is 26%, and the calculation result is counted in the total gas after air leakage, namely CO₂68% of water vapor, 3.5% of oxygen, 8.5% of nitrogen and SO₂Content 0.23%, after dehydration, CO₂The concentration is 81 percent, the emissivity of the three-atom gas of the high-temperature superheater is 0.297, the radiation attenuation coefficient of the three-atom gas is 5.31, the blackness of the flue gas is 0.37, and the radiation heat transfer coefficient of the flue gas is 111.4w/m²·℃。

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (4)

1. A method for acquiring the thermal performance of an oxygen-enriched combustion boiler comprises the following steps: fuel combustion calculation, flue gas and air supply simulation, heat balance calculation, hearth thermodynamic calculation and convection heating surface thermodynamic calculation,

wherein the furnace thermodynamic calculation comprises the steps of:

(A1) calculating the structural size of a hearth and the thickness of a relative radiation layer of the flue gas;

(A2) selecting the temperature of hot air, and calculating the effective heating value of each kilogram of fuel entering a hearth;

(A3) calculating the central position coefficient of the flame according to the general fuel class, the combustion equipment form and the arrangement mode;

(A4) estimating the temperature of the smoke at the outlet of the hearth, and calculating the average heat capacity of the smoke of the hearth;

(A5) calculating the radiation heat exchange characteristic parameter of the heating surface of the hearth;

(A6) calculating flame blackness and hearth blackness according to fuel and a combustion mode;

(A7) calculating and checking the temperature of the flue gas at the outlet of the hearth;

(A8) checking the error of the temperature of the smoke at the outlet of the hearth;

(A9) calculating the thermal parameters of the hearth;

(A10) calculating heat exchange of other radiation heating surfaces in the hearth;

the convection heating surface thermodynamic calculation comprises the following steps:

(B1) estimating the temperature of flue gas at the outlet of the heating surface, and checking a corresponding enthalpy value;

(B2) calculating the convection heat transfer quantity according to the outlet smoke enthalpy;

(B3) according to the principle that the side heat release quantity of the flue gas is equal to the side heat absorption quantity of the working medium, the enthalpy value and the corresponding temperature of the working medium outlet are obtained;

(B4) calculating the average convection heat transfer temperature difference;

(B5) calculating the convection heat release coefficient of the flue gas side and the pipe wall fouling coefficient;

(B6) calculating the convection heat release coefficient of the working medium side;

(B7) calculating the temperature of the pipe wall fouling layer;

(B8) calculating the blackness of the flue gas and determining the radiation heat release coefficient of the flue gas side;

(B9) calculating the total convection heat release coefficient;

(B10) calculating the convection heat transfer quantity;

wherein the radiation reduction coefficient of the triatomic gas used in the steps (A6) and (B8) is k_yInstead, it is calculated according to the following formula:

$k_y=-\frac{Ln(1-\mathrm{\ϵ})}{P_{H2O}S}$

wherein, P_H2OFor H in flue gas₂Partial pressure of O; s is the effective thickness of the radiation layer; is the three-atom gas emissivity; under the conditions of a certain temperature T and the effective thickness S of the radiation layer, the emissivity of the three-atom gas is calculated according to the following formula:

$\mathrm{\ϵ}(T,S)=\underset{j=1}{\overset{4}{\Σ}}{\mathrm{\α}}_j\left(T\right)(1-e^{-(p_{co2}+p_{H2o})k_j(T,\mathrm{\Φ})100S})$

${\mathrm{\α}}_j\left(T\right)=\underset{i=1}{\overset{4}{\Σ}}{c}_{j,i}{\left(\frac{T}{T_{ref}}\right)}^{I-i}$

$k_j\left(T\right)=\underset{i=1}{\overset{4}{\Σ}}{b}_i{\left(\frac{T}{T_{ref}}\right)}^{I-i}$

wherein p is_co2Is the partial pressure of carbon dioxide gas, p_H2OIs the water vapor partial pressure; phi is water vapor and dioxygenCarbon partial pressure ratio of phi P_H2O/P_CO2；T_ref1000K; t is the average Kelvin temperature of the flue gas; j is an integer, j is more than or equal to 1 and less than or equal to 4;

simulating the existing flue gas and air supply, and replacing the simulation with oxygen-enriched flue gas and air balance calculation, wherein the oxygen-enriched flue gas and air balance calculation is carried out according to the selected circulation multiplying power, air separation oxygen generation purity, peroxide coefficient, air leakage coefficient, condensed water vapor content, primary air share, hot air share in primary air and primary air oxygen injection proportion, and according to fuel components, setting initialized flue gas amount and iteration times, and adopting an iterative calculation method to obtain flue gas amount, smoke discharge amount, circulating flue gas amount, combustion-supporting gas primary air quantity, combustion-supporting gas secondary air quantity, air supply amount and air leakage quantity of an air separation device, and finally obtaining the flue gas amount, smoke discharge amount, circulating flue gas amount, combustion-supporting gas primary air quantity, combustion-supporting gas secondary air quantity, air supply amount and air leakage quantity of the air separation device by iterative calculation at last time as final;

the ith iterative calculation procedure is as follows:

amount of circulating flue gas V_ref：

V_ref＝V_i-1×R^r

Wherein, V_i-1Is the smoke amount obtained by the last iteration calculation, and when i is equal to 1, V is_i-1The initial smoke amount; r^rThe circulation multiplying power is adopted;

flue gas volume V_i：

$V_i=(1+{\mathrm{\α}}_{lf})(V_{ll}+V_{ref}+V_{o2}^0)$

Wherein α_lfThe air leakage coefficient; v_llThe theoretical smoke quantity generated by boiler combustion; v_refThe amount of the circulating flue gas is;the theoretical oxygen demand is calculated as follows:

$V_{o2}^0=1.866\frac{C_{ar}}{100}+5.56\frac{H_y}{100}+0.7\frac{S_y}{100}-0.7\frac{O_y}{100}$

wherein, Car, Har, Nar, Oar and Sar are the received base components of various elements in the fuel respectively;

discharge amount V_py：

V_py＝V_i-V_ref-V_lns

Wherein, V_lnsIs the water vapor content after condensation;

primary air volume V of combustion-supporting gas_zr1：

V_zr1＝β₁×V_ref

Combustion-supporting gas secondary air volume V_zr2：

V_zr2＝(1-β₁)×V_ref

Wherein, β₁Is the primary air share;

air supply volume V of air separation device_kf：

$V_{kf}=(V_{o2}-V_{o2}^{zr})/\mathrm{\γ}$

Wherein, V_o2The oxygen demand of the oxygen-enriched combustion boiler is obtained;the oxygen content originally contained in the combustion-supporting gas; gamma is the air separation oxygen production purity; oxygen demand V of oxygen-enriched combustion boiler_o2The calculation formula of (2) is as follows:

$V_{o2}={\mathrm{\α}}_{gy}\×V_{o2}^0$

wherein, α_gyIs the peroxide coefficient;theoretical oxygen demand;

air leakage rate V_lfThe calculation formula of (a) is as follows:

V_lf＝α_lf×V_O

wherein, α_lfThe value of the air leakage coefficient is less than 0.02, V_OThe calculation method is as follows for the amount of the flue gas at the outlet of the hearth:

$V_o=V_{ll}+V_{zr1}+V_{zr2}-V_{O2}^0$

wherein, V_llTheoretical amount of flue gas, V, produced for boiler combustion_zr1The primary air quantity of combustion-supporting gas, V_zr2The secondary air quantity of the combustion-supporting gas,is the theoretical requirement;

the gas leaking into the furnace chamber contains N₂、O₂、H₂O, the content of each component is calculated as follows:

$V_{N2}^{lf}=0.79\×V_{lf}$

$V_{O2}^{lf}=0.21\×V_{lf}$

$V_{H2o}^{lf}=0.161\×V_{lf}$

wherein,respectively N leaking into the furnace₂、O₂、H₂Volume of O.

2. An oxycombustion boiler thermal performance obtaining method according to claim 1, wherein the convective heat transfer coefficient when the convective heat transfer amount is calculated in step (B5) is calculated according to the following formula:

${\mathrm{\α}}_d=0.2C_z{C}_s\frac{\mathrm{\λ}}{d}{\left(\frac{\mathrm{\ω}d}{v}\right)}^{0.65}{P_r}^{0.33}$

wherein, C_z、C_sIn order to correct the coefficient, lambda is the heat conductivity coefficient of the flue gas; d is the pipe diameter; omega is the flow rate of the flue gas; upsilon is kinematic viscosity; pr is the prandtl number.

3. An oxygen-enriched combustion boiler thermal performance obtaining method as claimed in claim 2, wherein the kinematic viscosity upsilon and the prandtl number Pr are calculated according to the following formula:

$\mathrm{\υ}=\mathrm{\μ}\frac{R_{g}T}{p}$

$P_r=\frac{\mathrm{\μ}Cp}{\mathrm{\λ}}$

wherein mu is the dynamic viscosity of the flue gas, R_gIs the gas constant, T is the Kelvin temperature, p is the flue gas pressure, C_pThe specific heat capacity is the constant pressure of the flue gas, and the lambda is the heat conductivity coefficient of the flue gas.

4. An oxycombustion boiler thermodynamic property obtaining method according to claim 3, characterized in that the flue gas dynamic viscosity μ, flue gas constant pressure specific heat capacity C_pThe fitting method comprises the following steps:

smoke dynamic viscosity μ:

$\mathrm{\μ}=\frac{{\mathrm{\Σy}}_i{\mathrm{\μ}}_i{M}_i^{\frac{1}{2}}}{{\mathrm{\Σy}}_i{M}_1^{\frac{1}{2}}}$

flue gas constant pressure specific heat capacity C_p：

C_p＝y_iC_pi

Heat conductivity of flue gas λ:

$\mathrm{\λ}=\frac{{\mathrm{\Σy}}_1{\mathrm{\λ}}_i{M}_i^{\frac{1}{3}}}{{\mathrm{\Σy}}_i{M}_i^{\frac{1}{3}}}$

wherein, mu_iIs the kinetic viscosity of the pure i component under normal pressure; lambda [ alpha ]_iThe thermal conductivity coefficient of the pure i component under normal pressure; m_iIs the molar mass of the i component in the mixture; y is_iIs the molar fraction or volume fraction of the i component in the mixture, C_piIs the constant pressure specific heat capacity of the i component in the mixture.